BMW "No Reverse" Transmission Problem
An automatic transmission is that- automatic, consequently most people tend to pay very little attention to it until a major issue rears its ugly head.
Picture the scenario- you are driving along in the lap of luxury, the satellite radio blaring & the heated seats on. You have become accustomed to the comfort level & great driving experience brought to you by BMW.
You choose to cease at the local convenience store on your way home to grab some ice cream for the babies & a bottle of water for yourself. On returning to your automobile, you start it up, check your rearview mirror, put the shifter in reverse & then the unthinkable happens- the engine revs as if it is in neutral & the automobile goes nowhere!
This editorial deals with the reasons behind an unexpected loss of reverse in positive BMW automatic transmission equipped vehicles, specifically the three series & five series vehicles that use the ZF5HP19 or steptronic transmission. This includes the popular 323i, 323ci, 325i, 328i, 330i, 525i, 528i, 530i, X3 & X5 models well as some others built in the 1999 to present model years.
To eliminate confusion, this does not apply to vehicles equipped with the GM 5L40 E transmission, the ones with the sometimes problematic ZF5HP19. The 5L40 E has some issues of its own that are beyond the scope of this editorial but are definitely going to be the subject of another.
The failure rate for these transmissions appears to be high & is expected to become much more of an issue as time goes by.
Usually, the vehicle is working perfectly while driving forward but when it is put in reverse there is
complete & permanent loss of movement to back up.
Ads by Google
Reverse is usually a major feat for any transmission to accomplish- imagine the demands that are placed on a gearbox as it is asked to reverse the torque of your engine so that you can back up your 4000 pound vehicle.
The nice news is that there is hope in regards to a proper repair. The factory has released an updated part that so far appears to be a permanent fix for this issue.
By far, the most common cause of the reverse issue in BMW's is the failure of the D-G clutch drum. Specifically, the snap ring that retains the D or reverse clutch breaks out of the clutch drum leading to an inability for the clutch pack to apply.
In our testing & together with several hundred successful repairs at our facilities, the new part appears to be metallurgically superior in several ways.
They have found that there is an improved radius area as well as slightly thicker casting. In addition to this, the grove that retains the snap ring is also relocated further away from the fringe of the drum.
With this issue addressed & attention to detail in several other areas of the ZF5HP19 unit, the transmission can be repaired to "better than new" condition by a competent transmission rebuilder / remanufacturer. In fact, when properly repaired, the ZF gearbox becomes robust & can provide an indefinite service life.
ليست هناك تعليقات:
إرسال تعليق